Boolean Difference function adding new face unexpectedly
You can't create a face within a face without edges that connect this inner face to the outer face, thus the edges you're showing, otherwise the outer face will overlap the inner face, meaning the inner face couldn't exist, or it could exist but it wouldn't be part of the same mesh. As for your texture question, I don't see in what way it will cause any issue, just select the front faces and unwrap.